Water is the most essential component of life. However, with the growing scarcity of clean water, more and more interest is being paid to extraction of clean water from seawater and industrial water and to treatment of industrial process water and difficult wastewater streams. There is also an interest in the possibility of gentle water extraction from valuable solutions—from food streams to solutions of proteins and peptides or valuable small organic compounds.
Among different water purification techniques, reverse osmosis, forward osmosis and nanofiltration have become popular for water extraction because of their effectiveness in removing low molecular weight solutes, such as small organic compounds and ions. However, these water extraction techniques are still energy-intensive and not always sufficiently selective. Examples are contaminants, such as dissolved boron compounds naturally present in seawater and in contaminated groundwater, and which can pose a problem in desalinated water for irrigation and drinking water, and arsenic compounds that are frequently present in natural surface and ground water sources, e.g. in alluvial plains and moraine deposits.
Kim et al. 2012 studied boron rejection in various FO and RO water filtration experiments and found a maximum boron retention of about 50 to 55% in FO mode. However, this low boron filtration efficiency may necessitate several filtration cycles in order to obtain a desired low boron content in the resulting filtrate. Thus it is crucial to develop improved water extraction systems, such as systems that are able to remove water contaminants, such as boron or arsenic, and preferably in few or only one filtration step(s). In addition, it is a purpose of the invention to provide a water extraction system adapted for fertilizer drawn forward osmosis (FDFO), where seawater, brackish water, impaired ground or surface water or any other suitable water source can be used as a feed solution and a concentrated inorganic plant nutrient solution is used as a draw solution resulting in a final fertilizer solution having a sufficiently low osmolality or boron content as to allow it to be used as a liquid fertilizer, e.g. as irrigation water with added nutrients. Moreover, it is a purpose of the invention to provide a novel system for energy storage as well as a novel system for reuse of water, such as ultrapure water, in hemodialysis.